tpm/st33zp24/spi: Improve st33zp24_spi_evaluate_latency

Add check in st33zp24_spi_evaluate_latency helping to diagnose if the chip
is present or in a bad state.

Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

diff --git a/drivers/char/tpm/st33zp24/spi.c b/drivers/char/tpm/st33zp24/spi.c
index 08e6bf5..a2ef8ec 100644 (file)
--- a/drivers/char/tpm/st33zp24/spi.c
+++ b/drivers/char/tpm/st33zp24/spi.c
@@ -214,6 +214,11 @@ static int st33zp24_spi_evaluate_latency(void *phy_id)
                                                &data, 1);
                latency++;
        }
+       if (status < 0)
+               return status;
+       if (latency == MAX_SPI_LATENCY)
+               return -ENODEV;
+
        return latency - 1;
 } /* evaluate_latency() */